The present invention relates generally to communications systems, and more particularly, to an assignment system for assigning users system resource s particularly suitable for mobile applications.
In this communication age, content providers are increasingly investigating ways in which to provide more content to users as well as interfacing with users.
Communication satellites have become commonplace for use in many types of communication services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. As such, satellites transmit and receive large amounts of signals used in either a xe2x80x9cbent pipexe2x80x9d or xe2x80x9cspot arrayxe2x80x9d configuration to transmit signals to desired geographic locations on the earth.
Because the frequency of resources is scarce for over-the-air transmission, various encoding schemes are used to provide a greater number of communication signals within an allocated communication band. Such encoding schemes include code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), or combination of these schemes. Further, to prevent interference the schemes may operate at various frequencies.
CDMA systems are commonly used in mobile applications. In the mobile applications a plurality of base stations are positioned to provide coverage for a cell of a service area. Each of the base stations has a plurality of orthogonal codes that are used in each base station. The same group of orthogonal codes are reused in a cell covered by another base station a predetermined distance away. No central code management resource is needed because the base station with the same orthogonal codes is located sufficient distance so that interference does not occur. As the mobile user travels throughout the service area, frequency switching must occur often as the user travels into the range of another base station. Frequency switching may cause inconvenience such as discontinuity during switching time. Also, the additional signaling required for frequency switching adds to higher overhead in the system.
It would therefore be desirable to provide a resource assignment scheme that reduces the amount of switching of users.
It is therefore one object of the invention to provide an improved resource assignment scheme that reduces switching of resources between users while allowing an increased number of users.
In one aspect of the invention, a method for operating a communication system comprises the steps of:
assigning a first resource to a first beam of a first mobile user, defining a first interference contour around said first mobile user;
assigning a first resource to a second beam of a second user;
defining a second interference contour around said second user;
moving the first beam and first interference contour with the mobile user;
continually determining whether an interference occurs between the first beam and the second beam by determining whether the first interference contour intersects the second interference contour; and,
when the first interference contour intersects the second interference contour, declaring an interference and reassigning a second resource to the first beam.
In a further aspect of the invention, a communications system includes a high altitude communication device that communicates with a plurality of user terminals and a gateway station. The gateway station couples the users to terrestrial networks and other users. The high altitude communication device has gateway station that assigns a first code to a beam of a first plurality of users. The gateway station continually determines whether an interference occurs between the first beam and the second beam by determining whether the first interference contour intersects the second interference contour when an the first interference contour intersects the second interference contour. The gateway declares an interference when the contours intersect and reassigns a second resource to the first beam.
One advantage of the invention is that the complexity of the overall system is reduced and thereby the overall system cost is reduced. By reducing the complexity the weight of the payload for the high altitude communications device is also reduced.